While a general literature review indicates that agricultural fungal inoculants are extremely
promising, success remains mixed in part due to diversity of crops, and a variety of inoculants and application methods. In part because the majority of research has been done on single species plants or fungus, or in greenhouses, there is even less research providing application guidelines for farmers with polyculture field applications. SARE has provided several grants to farmers working on inoculation with mixed results; one of the most promising, Farm-Grown Microbial Soil Inoculants [on wheat] indicated: “only the on-farm inoculant produced measureable increases in nutrient update and crop growth, demonstrating that on-farm produced inoculants can be effective alternative to purchased, commercial inoculants, and may reduce the need for chemical fertilizer.”(4) While another SARE grant “On-Farm production of mycorrhizal fungus inocula” found some success, they
note the difficulties of on-farm IMO production presented several limitations, “we have seen that even incorporating [Arbuscular mycorrhizal] fungus inoculum into greenhouse practice is a large step not fully accomplished within the 4 growing seasons of this project, so the consideration of the symbiosis in the whole of farm operations is likely far off.”(5) In my literature review, no field trials studying this particular method of IMO (based on a Korean Natural Farming method) have been found, nor focused on polyculture inoculation at time of transplantation.
Promising research on the benefits of fungal inoculants in disease resistance includes: against soil-borne diseases, against nematodes, and some specific crops and diseases. Downy mildew control in sweet basil continues to be an area of research, but with limited success in finding organic control methods. Control of disease causing oomycetes (such as Peronospora belbahrii) with fungal inoculant has primarily been lab-based work, but holds promise “[this] opens up exciting possibilities for investigating the commonalities and differences between pathogenic and mutualistic lifestyles.”(6) Another conceivable benefit of this specific IMO protocol holds some promise, as the Arbuscular mycorrhizal fungi (AMF) associated mechanisms “might thus act in synergy with each other, with one mechanism becoming preponderant depending on the environmental conditions and the plant-cultivar pathogen/AM fungus strain studied.”(7)
Agricultural fungal inoculant research has been fairly narrowly focused on several species/families, especially fabaceae, with a need for work on a diversity of crops. Each of the five crops chosen shows promise of benefits with inoculation.
Sweet basil (Ocimum basilicum): AMF symbiosis may induce production of two important
phytochemicals: rosmarinic and caffeic acids, “AMF potentially represents an alternative way of promoting growth of this important medicinal herb, as natural ways of growing such crops are currently highly sought after in the herbal industry.”(8) This grant will build on other SARE grants on downy mildew, including using modified assessment methodology established by Joan Allen.
Notably, research has found that fungal endophytes in related Ocimum sanctum “hold great promise … as biocontrol agents against broad spectrum and economically significant phytopathogens.”(9)
Ashwagandha (Withania somnifera): may be unfamiliar to some vegetable growers, but is a
prominent Ayurvedic medicinal herb, widely used for thousands of years. It can be readily grown in the Northeast, and has huge sales growth potential. Ashwagandha had the highest growth (40.9%) between 2014 and 2015 of any herb though natural channel sales.(10) AMF inoculation in field trials has shown benefits: enhanced shoot and root length, biomass, overall size, number of inflorescences and flower, seed production and net primary productivity.(11)
Onions (Allium cepa) are regarded as highly AMF responsive plants. Initial research indicates increases in nutrition and synergistic effect with dual microbial inoculation; one study showed nearly 100% increase in bulb fresh weight with Glomus sp. inoculum.(12) Onion is the third most consumed fresh vegetable in the United States, but also valued for medicinal qualities.
Fennel (Foeniculum vulgare): is a valuable crop both as vegetable, medicinal herb and for
value-added products. Its cultivation area has increased four times during the past two decades and mycorrhizal inoculation has been shown to improve quantitative and qualitative yield, especially under drought conditions.(13)
Parsley (Petroselinum crispum): AMF inoculation of parsley has been shown to increase root and shoot biomass as well as improve chlorophyll content.(14) Parsley is also a familiar crop that is grown by vegetable and herb farmers alike.
My proposed solution is to design an on-farm research study using fungal inoculants to examine two concrete benefits to farmers: increased marketable crop yield and downy mildew disease resistance in sweet basil. My research will use a randomized block design method with five transplanted crops of commercial value (onions, sweet basil, ashwagandha, fennel, and parsley). The design will compare yields of these five crops and basil downy mildew disease resistance using a simplified on-farm indigenous microorganism inoculant, compared with a commercial inoculant, compared with a control. These two straightforward, measurable benefits of crop yield and disease resistance can then be readily shared with other Northeast farmers to allow them to decide whether to implement similar IMO or commercial inoculant practices. All crops chosen are medicinal herbs currently grown by this farmer but also of potential interest to vegetable growers; all crops also have at least one prior study indicating a plant species/fungal symbiosis benefit. If benefits are shown, a simplified IMO protocol can then be provided to other farmers to utilize. This grant would further knowledge on a sustainable production method that is potentially profitable, environmentally sound and beneficial to the wider farm community.
Melody Wright 2016 SARE Endnotes
1. McCoy, Peter. (2016) Radical Mycology: A Treatise on Seeing and Working with
2. Kumar, B.L., Gopal D.V.R. (2015) Biotech. “Effective role of indigenous
microorganisms for sustainable environment.”
3. Berruti, A., Lumini, E., Balestrini, R., Bianciotto, V. (2016) Frontiers in
Microbiology. “Arbuscular Mycorrhizal Fungi as Natural Biofertilizers: Let’s Benefit
from Past Successes.
4. Englander, Aaron. (2013 end date). SARE program. “Farm-Grown Microbial Soil
Inoculants: Effects on Bread Wheat Yield and Quality.”
5. Douds, Jr., David. (2007 end date). SARE program. “On‐farm production of
mycorrhizal fungus inocula.”
6. Fawke, S., Coumane, M., Schornack, S. (2015) Microbiol Mol Biol Rev. “Oomycete
Interactions with Plants: Infection Strategies and Resistance Principles.”
7. Lioussanne, L. (2010). Spanish Journal of Agricultural Research. “Review. The role
of the arbuscular mycorrhiza-associated rhizobacteria in the biocontrol of soilborne
8. Toussaint, J.P., Smith, F.A., Smith, S.E. (2007). Mycorrhiza. “Arbuscular
mycorrhizal fungi can induce the production of phytochemicals in sweet basil
irrespective of phosphorus nutrition.”
9. Chowdhary, K., Kaushik, N. (2015). PLOS One. “Fungal Endophyte Diversity and
Bioactivity in the Indian Medicinal Plant Ocimum sanctum.”
10. American Botanical Council
11. Rai, M., Acharya, D., Singh, A. (2001). Mycorrhiza. “Positive growth responses of
the medicinal plants Spilanthes calva and Withania somnifera to inoculation by
Piriformospora indica in a field trial.
12. Albrechtova, J., Latr, A., Nedorost, L., Pokluda, R., Posta, K., Vosatka, M. (2012).
The Scientific World Journal. “Dual Inoculation with Mycorrhizal and Saprotrophic
Fungi Applicable in Sustainable Cultivation Improves the Yield and Nutritive Value
13. Zardak., S.G., Dehnavi, M.M., Salehi, A., Gholamhoseini, M. (2016). Journal of
Applied Research on Medicinal and Aromatic Plants. “Response of field grown
fennel (Foeniculum vulgare Mill.) to different mycorrhiza species under varying
intensities of drought stress.”
14. Regvar, M., Vogel-Mikus, K. (2003) Folia Geobotanica. “Effect of AMF inoculum
from field isolates on the yield of green pepper, parsley, carrot, and tomato.”
My proposed solution is to design an on-farm research study using fungal inoculants to examine two concrete benefits to farmers: increased marketable crop yield and downy mildew disease resistance in sweet basil. My research will use a randomized block design method with five transplanted crops of commercial value (onions, sweet basil, ashwagandha, fennel, and parsley). The design will compare yields of these five crops and basil downy mildew disease resistance using a simplified on-farm indigenous microorganism inoculant, compared with a commercial inoculant, compared with a control. These two straightforward, measurable benefits of crop yield and disease resistance can then be readily shared with other Northeast farmers to allow them to decide whether to
implement similar IMO or commercial inoculant practices. All crops chosen are medicinal herbs currently grown by this farmer but also of potential interest to vegetable growers; all crops also have at least one prior study indicating a plant species/fungal symbiosis benefit. If benefits are shown, a simplified IMO protocol can then be provided to other farmers to utilize. This grant would further knowledge on a sustainable production method that is potentially profitable, environmentally sound and beneficial to the wider farm community.
CROP YIELD PROTOCOL:
- Seeds were purchased from High Mowing and Simply Medicinals were started in greenhouse flats with commercial potting soil. 100 seedlings of each of the five crops are seeded. At the time of transplantation 60 seedlings were selected, with 10 seedlings each assigned one of three treatments, and each treatment duplicated (see attached design excel document). An additional 60 sweet basil seedlings are started with 40 selected for the disease resistance protocol (see below). Approximate seeding dates:
Onion (Allium cepa, Yankee F1): Due to low germination rates of original seeding, onion sets were substituted on planting day
Ashwagandha (Withania somnifera): 3/19/17 (potted up 4/20/17)
Parsley (Petroselinum crispum, Italian flat leaf): 3/19/17
Fennel (Foeniculum vulgare, Finale): 4/13/17. Due to low germination rates, 7 instead of 10 plants were used in each treatment
Sweet Basil (Ocimum basilicum, Genovese): 4/13/17
- Eleven new beds were built (11’x4’). Research strongly suggests that this farm’s prior inoculation trials could have significant impact on yield and disease resistance findings, so new un-inoculated beds are essential. Beds are in close proximity with similar sun exposure, in a grass-lawn area not cropped in 2016, and bordered by rough sawn timber to prevent lateral migration of fungi between treatments.
- A reference soil sample was sent to Logan Labs before inoculation. As low organic matter is expected, commercially purchased organic compost was added at the low rate of 2 cubic foot/bed. A low rate is used as research suggests excessive added nutrients likely would suppress fungal growth.
- After last frost, on June 1, 2017 seedlings were transplanted in a block design identical for each treatment bed. Running from East to West: each bed was planted in order with Ashwaganda, Parsley, Basil, Fennel and Onions.
- T1: control with no treatment
- T2: MycoGrow purchased from Fungi Perfect, used according to instructions. 1 oz added per each gallon of water for root drenching at time of transplant. Contains Glomus intraradices, Glomus mosseae, Glomus aggregatum and Glomus etunicatum
- T3: On-farm produced Indigenous Microorganism inoculant (see below) is added to the soil just prior to seedling transplantation
- At transplantation, all seedlings received a root drenching with a brief dip in separate buckets. T1 well water, T2 MycoGrow in well water, and T3 well water. All transplants were then mulched with commercially purchased straw and watered again with T1, T2, or T3 water. Mulching is important to keep the inoculants hydrated and alive.
- Beds were hand weeded and watered equally with overhead irrigation as needed. Monthly rainfall data from NOAA is also recorded, for future reference if unusual precipitation trends occur.
- Each crop was harvested when mature by days to maturity (DTM), final visual assessment, and with CSA distribution schedule. For each crop, each plot within each bed (T1, T1, T2, T2, T3, T3) is harvested, weighed and recorded independently.
- Onion: Sept 22, 2017 bulb
- Ashwagandha: Sept 24, 2017 roots only (tops discarded)
- Fennel: August 16, 2017 shoot
- Parsley: August 3, 2017 shoot
- Sweet Basil: July 20, 2017 shoot
BASIL DOWNY MILDEW PROCOTOL:
- Using the additional 40 sweet basil seedlings, five seedlings were assigned to T1,T1, T2, T2, T3, T3, T4, and T4, using the above protocols.
- T4 is a repeat IMO application and is known to farmer. For T4, the IMO inoculant is applied at transplant and additional side dressing to each plant (1/2 cup Stage 4 IMO) weekly. The remainder of the T4 beds are planted with onions. Since onions are already part of the study and randomly planted throughout the beds, this crop should have no impact on findings. The extra onions are not included in data collection.
- Downy mildew disease pressure is expected from naturally occurring inoculum, typically July/August. Each sweet basil plant in this protocol is visually inspected weekly for downy mildew. Disease incidence is measured by counting the number of plants in each treatment protocol for downy mildew. Disease severity is rated using system adapted from SARE grant Allen, 2011.
0= no symptoms
1= symptoms noted with 1-10% leaf area with sporulation
2= symptoms noted with > 10% leaf area with sporulation
Statistical analysis of data is budgeted and completed by Dr. Maura Bozeman, Academic Program Manager of Environmental Sciences at Post University. Although a complex economic analysis is beyond the scope of this project, costs of commercial inoculant versus cost of producing on-farm IMO are shared with farmers at outreach.